The invention relates generally to transducers, and more specifically to a transducer assembly for real-time three-dimensional imaging in space-critical applications.
Transducers, such as acoustic transducers, have found application in medical imaging where an acoustic probe is held against a patient and the probe transmits and receives ultrasound waves, which in turn may facilitate the imaging of the internal tissues of the patient. For example, transducers may be employed to image the heart of the patient.
Heart rhythm problems or cardiac arrhythmias are a major cause of mortality and morbidity. Atrial fibrillation is one of the most common sustained cardiac arrhythmias encountered in clinical practice. Cardiac electrophysiology has evolved into a clinical tool to diagnose these cardiac arrhythmias. As will be appreciated, during electrophysiological studies, probes, such as multipolar catheters, are positioned inside the anatomy, such as the heart, and electrical recordings are made from the different chambers of the heart.
Catheter-based techniques used in interventional procedures generally involve inserting a probe, such as an imaging catheter, into a vein, such as the femoral vein. Unfortunately, conventional cardiac interventional procedures such as ablation of atrial fibrillation are complicated due to the lack of an efficient method to visualize interventional devices and cardiac anatomy in real-time.
Techniques, such as transthoracic imaging have been employed to overcome the drawbacks of the conventional cardiac interventional procedures. Transthoracic imaging techniques typically necessitate placement of a transceiver against the chest of a patient and the use of this transceiver to image the heart. However, the presence of bones and other tissue types interposed between the transceiver and the heart during the transthoracic imaging procedure prevents the formation of a sufficiently detailed image of the heart. Alternate techniques such as transesophageal imaging procedures have also been utilized to facilitate imaging of the heart. These transesophageal techniques typically involve the insertion of a transceiver into the esophagus of the patient. Although transesophageal imaging positions the transceiver closer to the heart, a drawback of this procedure is that transesophageal imaging necessitates rendering the patient unconscious by way of a general anesthetic. However, as will be appreciated, it is highly desirable to have a conscious patient to facilitate imaging of the heart.
The drawbacks associated with the above mentioned techniques may be circumvented via the use of intracardiac echocardiography (ICE). Intracardiac echocardiography is an emerging catheter imaging technology employed to guide interventional procedures such as catheter positioning and ablation, for example. Furthermore, intracardiac echocardiography typically uses sound waves to produce images of the heart. Additionally, with intracardiac echocardiography, a probe, such as a miniaturized ultrasound tipped catheter, may be utilized to obtain images of the heart.
Unfortunately, currently available commercial catheter-based intracardiac probes are restricted to two-dimensional imaging. For example, presently available commercial catheter-based intracardiac probes used for clinical ultrasound B-scan imaging suffer from limitations associated with the monoplanar nature of the B-scan images.
A typical probe, such as an ultrasound probe, typically includes a transducer package, a multi-wire cable connecting the transducer to the rest of an imaging system, such as an ultrasound system, and other miscellaneous mechanical hardware such as the probe housing, thermal and/or acoustic potting material and electrical shielding. However, the high density of interconnections required to address each transducer element in a two-dimensional transducer array disadvantageously results in poor space efficiency of the transducer assemblies.
Previously available methods of fabricating transducer arrays have incorporated multi-layer flexible interconnect circuits to facilitate coupling the plurality of transducer elements. These multi-layer flex circuits route conductors on multiple flexible layers parallel to the plane of the transducer elements. However, such interconnect circuits are expensive and fail to efficiently utilize space within a catheter. Additionally, acoustic performance of transducers fabricated with such methods has suffered due to the presence of an acoustically unfavorable interconnect circuit immediately underneath the active elements. Disadvantageously, many previous attempts to facilitate space efficient interconnections of transducer elements have had limited effect on imaging performance of the catheters.
There is therefore a need for a transducer assembly capable of real-time three-dimensional imaging for use in a probe employed in space critical applications such as intracardiac imaging. In particular there is a significant need for a design of a transducer assembly that advantageously enhances the imaging performance of a probe while maximizing the aperture. Also, it would be desirable to develop a simple and cost-effective method of fabricating a transducer assembly capable of real-time three-dimensional imaging.